tests/test-hardlinks-safety.out

cmdutil: changeset_printer: use methods of filectx/changectx.

This allows extensions that modify changeset metadata (e.g.
description) by overriding methods of changectx to get consistent
behavior from all log-like commands, regardless of whether templates
or styles are used. Without this, overriding changectx methods works
if you use styles or templates, but not with default log format.

This meant adding filectx.extra() for consistency with changectx.

% no diff if hardlink
% init
adding foo to series file
applying foo
now at: foo
adding bar to series file
applying bar
now at: bar
430ed4828a74fa4047bc816a25500f7472ab4bfe:foo
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c:bar
%
foo
bar
%%%
430ed4828a74fa4047bc816a25500f7472ab4bfe:foo
%
foo
patch foo finalized without changeset message
patch bar finalized without changeset message
%%%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo
430ed4828a74fa4047bc816a25500f7472ab4bfe bar
%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo
430ed4828a74fa4047bc816a25500f7472ab4bfe lbar
%%%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo
%
4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo